TRANSIT MK7 BROKEN ENGINE MOUNTS

I've just forked out some £225 to replace the gearbox end mountings which had broken away when the bolts sheared. Fortunately no other damage was done, and even more fortunately, it happened within 200 yards of my SIL's house at the end of their summer holiday and he was able to arrange a swift and effective repair. Is this breakage a common fault, or is it that I'm just unlucky? This is the first repair on the MH since I bought it new in May 2011.